Functional Assessment in Greek Tension-Type Headache Sufferers: Validity, Reliability, Responsiveness and Psychometrics of the Migraine Disability Assessment Questionnaire (MIDAS)

Introduction: Functional assessment in painful musculoskeletal disorders such as tension-type headache requires valid, reliable and sensitive instruments. MIDAS (Migraine Disability Assessment questionnaire) is an internationally well-known functional index which has not been validated in Greek headache sufferers.
Aims: The aim of the study was to assess headache related disability in Greek tension-type headache sufferers using MIDAS. The validity, reliability, responsiveness and psychometrics of the Greek MIDAS version were examined.
Study Design: A multicenter prospective design was followed.
Place and Duration of Study: The study took place in a medical rehabilitation unit and two physiotherapy private practices in Athens, from January - December 2010.
Methodology: A sample of 121 patients(101 women, age: 39.4+12.7; 20men, age: 35.5 + 8.8, years) with tension-type headache was recruited. Internal consistency was computed and test-retest reliability was examined for a 7-day period. Responsiveness of the GR-MIDAS was tested before and after a behaviorally oriented physical therapy protocol. Convergent and divergent validity were also examined after comparing GR-MIDAS with SF-12, VAS, Pain Catastrophising Scale (PCS), Hospital Anxiety and Depression Scale (HAD) and Short-Form McGill Pain Questionnaire (SFMPQ).
Results: Cronbach’s alpha (α) was satisfactory (0.80). Test-retest reliability was both excellent for the total score (ICC=0.95) and the individual items (0.87-0.98). Measures of responsiveness such as the Standardized Effect Size (SES=1.38) and the Standardized Response Mean (SRM=1.63) were shown to be acceptable, as well as the ROC curve statistic (AUC: 0.875 +0.08). Convergent validity was evidenced (SF-12 vs MIDAS, r=-0.32, p<0.001), and also divergent validity [MIDAS vs VASaverage, r=0.31, p<0.01; MIDAS vs HAD: anxiety: r=0.17, NS, depression: r=016, NS; MIDAS vs PCS: r=0.13, NS; SFMPQ vs MIDAS: Affective: r=0.02, NS, Sensory: 0.11, NS].
Conclusion: The Greek version of MIDAS is a valid, reliable and sensitive functional measure for tension-type headache patients, comparable to the original version. The data of this study extend the psychometric properties of the instrument.